One technique commonly used in industry as part of a milling or machining process to hold a component, such as an airfoil for an aircraft, is referred to as “picture framing”. In machining the component, a center portion of a large billet or block of raw material, consisting typically of steel or aluminum, is machined to form the component. The block of material is oversized such that a predetermined amount of excess material exists around the outer perimeter of the center portion. This excess material forms a “frame” upon which clamps can be fastened to hold the block in place on a milling table during the machining process.
Although picture framing provides a simple technique for milling a component, it has associated disadvantages. One such disadvantage is the inclusion of the excess material to form the frame. The excess material needs to be recycled or discarded. For large parts this excess material is costly and can result in a significant amount of scrap.
In addition, picture framing can only be used when a piece of stock is available that is of proper size to accommodate for the dimensions of the component being machined, as well as for the required and associated framing dimensions. There are often incidents when the stock available is large enough to accommodate only the dimensions of the component and not of a frame. As a result, that component must be machined and assembled as multiple elements or cannot be machined until a billet of material of adequate size is ordered, shipped, and received. The machining and assembling of multiple elements, as opposed to a single unitary structure, can add undesired weight, costs, manufacturing time, and complexity to a system. The assembling or joining of elements reduces the strength of the resultant component, which can lead to fatigue cracks and corrosion.
Thus, there exists a need for an improved technique of holding a block of material to a machining table that does not have the above-stated and associated disadvantages.